European patent application 0,358,729 discloses a related device for mounting a motor vehicle tire on a wheel rim or removing it from a wheel rim, whereby the bearing support for the wheel rim has a pneumatic rotating drive and clamp arms that are spread by means of a pneumatic drive with respect to the upright axis which is aligned at a slight angle to the vertical and have pressure parts on their free ends that press from the inside against the bed of the wheel rim with a spreading motion. Due to the offset angle of the clamp arms, the wheel rim is automatically centered on the slightly inclined upright axis of the bearing support. The two arms of the pressure device which have the pressure elements are mounted on a vertical column so they pivot in the horizontal plane and are arranged so they can be advanced toward each other by means of a compressed air cylinder in the axial direction of the column. Each arm consists of a holder mounted on a column guide, where the holder is in the form of a sliding bushing, and a lever that is mounted with one end in this holder so it can rotate and has a pressure roll on its free end. A pressure cylinder arranged in the holder acts approximately on the middle section of the lever and exerts a compressive force on the lever across the longitudinal axis of the arm and thus also on the pressure roll, so the two levers of the two arms each execute a limited pivoting motion about their end bearings. At the upper end of the machine stand a buckling arm is mounted so it can be pivoted vertically and has a hook-shaped lifting element on its free end that acts on the tire bead from beneath when the buckling arm is moved by an operator and the lifting hook is pulled by hand over the horn of the wheel rim. By rotating the bearing support, the tire bead is released from the rim by this lifting hook. The primary disadvantage of this known mounting device is the inadequate adaptability to different types of tires and wheel rims. In addition, operation of the individual function groups requires a considerable amount of experience and skill on the part of the operator.
U.S. Pat. No. 4,047,553 discloses a mounting device for pneumatic tires having a column-like bearing support on a rigid bed with a conical clamping wheel held on the threaded spindle so it can rotate in order to secure the bowl of the tire. A vertical stand is adjustable in height like a telescope by means of a pressure cylinder and has two horizontal arms, the ends of which each have a conical pressure roll mounted on them. The pressure rolls can be advanced up to one side wall or the other in succession by means of vertical movements of the telescoping stand in order to force one tire bead or the other away from the horn of a wheel rim. This known mounting device also requires skilled personnel and can be used with different tire sizes and different types of wheel rims only to a limited extent. A similar mounting device for tires is also known from U.S. Pat. No. 3,086,578.
Another important disadvantage of all the known mounting devices is that the pressure elements that are designed as conical rolls made of plastic, for example, act directly on the relatively sensitive side walls of the tire in the pressing operation, which can lead to imperceptible damage to the interior of the tire, especially the radial body. Such damage must be avoided at all costs because it can have a very negative effect on the driving safety of the motor vehicle and can lead to sudden blowout of the tire at high speeds.